This invention relates to a pneumatic tire having an integrated circuit transponder located within the structure of the tire for use in tire identification and pressure data transmission. More particularly, the invention relates to the combination of a pressure transducer with a pneumatic tire and a transponder. The transponder is a passive device in that it has no source of electrical energy but instead depends upon the receipt of an "interrogation" signal emanating from a source outside of the tire. The interrogation signal is rectified by the circuitry in the integrated circuit transponder, which then utilizes the rectified signal as a source of electrical energy for use in its transmission of an electrical signal digitally encoded to identify the tire. A unique identification number or code can be used for each tire.
Reference is made to commonly-assigned U.S. Pat. No. 4,911,217 issued Mar. 27, 1990, to Dunn et al. which discloses a commercially-available integrated circuit transponder suitable for use in a pneumatic tire and which discloses an electric-field coupled interrogator/transponder system. The disclosure of U.S. Pat. No. 4,911,217 is incorporated herein by reference and is referred to below as the Dunn et al. patent.
An alternative integrated circuit is commercially available from Texas Instruments of Austin, Tex., and is sold under the name TIRIS.TM., for Texas Instruments Registration and Identification System. While these integrated circuits are not ideal, they are preferred because of their commercial availability. The integrated circuit disclosed in U.S. Pat. No. 4,911,217 also is preferred because it is the only integrated circuit that has been successfully tested in a location in a pneumatic tire enabling practice of the subject invention.
In the manufacture of pneumatic tires, it is desirable to provide unique numerical identification for each tire as soon as possible during the course of its fabrication. Also, the identification should be easily discernible throughout both the manufacturing process and the life of the tire, and retreading of the tire should not adversely affect identification. If the tire is mounted on a steel or aluminum wheel, as is the normal case, or on a dual wheel assembly, then the tire identification should still be easily acquired by tire owners and users for use in inventory control, record keeping and warranty determination. The ability to identify tires throughout their manufacture is particularly valuable in quality control because the source of manufacturing problems can be much more readily ascertained than is the case in the absence of specific tire identification. Statistical process control and other methods can be used with tire identification to detect process parameters that are going out of control or to detect machinery wear, failure, or maladjustment. These benefits of tire identification practically speaking cannot be obtained unless a radio-frequency transponder is available for incorporation in a tire. The transponder must be quite inexpensive, reliable, and readable from any position around the tire or vehicle wheel on which it is mounted: it also must survive manufacturing processes, be usable during the course of manufacture and must not adversely affect tire life or retreadability. In addition to providing tire identification with a transponder, it is desirable to transmit data concerning the pressure within the tire. This concept is described in EPA No. 0 301 127 dated Feb. 1, 1989 (column 14), which is assigned to Texas Instruments Deutchland GmbH and which is believed to describe the above-mentioned integrated circuit transponder of Texas Instruments.
Destron/IDI of Boulder, Colo. proposed a vehicle tire identification system described in the international application published under the Patent Cooperation Treaty as Publication No. W090/12474 dated Oct. 18, 1990. This published application, on page 8 and in claim 8, suggests the use of means for sensing the condition of a tire. The publication also references U.S. Pat. No. 4,730,188 to Milheiser, which describes a transponder similar to that disclosed in the Dunn et al patent.
The use of pressure transducers in pneumatic tires, in association with electronic circuitry for transmitting pressure data, is well known, as is exemplified by U.S. Pat. No. 4,578,992 to Galask. However, these pressure-data systems for tires have been plagued by difficulties inherent in the tire environment. Such difficulties include the rugged use the tire and electronic components must undergo, as well as the possibility of deleterious effects on the tire from incorporation of the pressure transducer and electronics in a tire/wheel system.
The invention enables these difficulties to be overcome, while also providing the desired tire numerical identification and data transmission from any position around the tire.